The Durability of an Organic–Inorganic Sol–Gel Interlayer in Al-GFRP-CFRP Laminates in a Saline Environment

Abstract

The aim of the study was to assess the selected properties of a hybrid organic–inorganic silane sol–gel coating (HSG) used in hybrid fiber metal laminates (FML) in a corrosion environment. The HSG coating on the aluminum alloy was produced using 3M™ AC130-2 formulation consisting of 3-glycidoxypropyl-trimethoxysilane (GPTMS) and tetra-n-propoxyzirconium (zirconium(IV) propoxide) (TPOZ). Laminates consisted of aluminum alloy AA2024-T3 sheets, with carbon fiber reinforced polymers (CFRPs) and a glass fiber reinforced metal–composite structure (GFRP). Potentiodynamic and polarization curve and impedance (EIS) tests were carried out on HSG at ambient temperatures after 1 h and 150 h of soaking. Neutral 0.5 M NaCl and 0.8 M NaCl solutions were used for open circuit potential (OCP) and potentiodynamic tests, and 0.5 NaCl was used for the EIS test. A neutral salt spray (NSS) test was applied to laminates with a 12 week exposure period. The results obtained revealed that the HSG coating did not provide sufficient protection against corrosion of the aluminum alloy in direct contact with an aggressive environment but was effective as an interlayer. Local aluminum sheet perforation did not lead to delamination at the metal–composite interface regardless of the type or configuration of the composite. This confirms the durability of HSG used in FMLs.

Short-beam shear fatigue life assessment of thermally cycled carbon–aluminium laminates with protective glass interlayers

“…Similar trends have been observed in authors previous studies for laminates with a different method of aluminium surface preparation [12,19] and in hygrothermal conditions by da Costa [20]. Significant effects of thermal shocks on GLARE [15,[31][32][33] and CARALL [34,35] laminates were only observed after more than 10,000 thermal cycles.…”

“…The surface of the sheets was coated with the organic-inorganic hybrid sol-gel 3 M Surface Pre-Treatment AC 130-2 two-component formulation (3 M, USA) as an adhesive film. See earlier publication for detailed information on the method of metal surface preparation and the used primer [12].…”

“…fuselage during standard operation (ascents and descents − 55 °C to + 70 °C, also anti-or deicing − 25 °C to + 80 °C) [15,18,20]. The detailed course of this research is described in other works [12,19].…”

“…Liu et al [9] and Peng et al [10] confirmed the establishment of a galvanic couple and associated corrosion when the aluminium alloy is coupled to the CFRP composite. For this reason, in recent years, some attempts have been made to separate carbon fibres from an aluminium alloy by introducing additional dielectric layers as structural adhesive [4], prepreg resin [7], glass fibres [11] and glass fibres with adhesives [12], or other materials, such as rubber [13], also replacing an aluminium alloy with titanium [14].…”

Corrosion Resistance in NaCl Environment of Fiber Metal Laminates based on Aluminum and Titanium Alloys with Carbon and Glass Fibers

“…It may be helpful to determine the potential in the open circuit potential (OCP) tested for each of the materials that make FML laminates. Such results are given, respectively, for titanium [ 16 ] and the work by Surowska et al [ 23–25 ] for fibers and aluminum anodized in SAA, whereas the previous study [ 26 ] gives the value for anodized aluminum in CAA.…”